Parshas Bamidbar

Many reasons are given for the tragic deaths of Nadav and Avihu. (See
Vayikro Rabbah 20:8,9)

Among the reasons more readily implicit in the Chumash are one in Parshas
Bamidbar and three in Sefer Vayikro. The reason in Parshas Bamidbar is for
not having married and fathered children (3:2). The three in Vayikro are
for having drunk wine prior to undertaking the Avodah and for having
paskened halacha in front of Moshe Rabbeynu, both derived in Parshas
Shmini (10:2; see Rashi), and also for having entered the Kodesh at a time
when they were not commanded to do so (Acharei Mos 16:1,2; see Rashi). Why
are some reasons given or derived in Sefer Vayikro and another is in Sefer
Bamidbar?

Along the same line, why are some karbanos (the musafim of Parshas
Pinchos, in particular) described only in Sefer Bamidbar - isn't Sefer
Vayikro the 'Toras Kohanim'? Put differently, what is the difference
between the karbanos taught in Sefer Vayikro and those taught in Sefer
Bamidbar?

The fundamental difference between Vayikro and Bamidbar is that Vayikro is
about the individual or Klal Yisroel drawing close to HKB'H
(korban=drawing close; Vayikro is a special expression of endearment - see
first Rashi on Vayikro), whereas Bamidbar is about the individual or Klal
Yisroel acting as an emissary of HKB'H to the outside world.

Bamidbar means 'in the desert', implying its subject matter is how we are
to address or orient ourselves toward the outside. The many events of
Sefer Bamidbar bear out this theme, from counting the people for army and
avodah purposes to sending emissaries to 'tour' the Land to interactions
with Balak, Bilam, Sichon, Emori, etc., all the way through and including
the events of the ultimate emissary, Pinchos (Pinchos=Eliyahu).

Accordingly, whereas the karbanos of Vayikro are designed exclusively to
bring us close to HKB'H, the karbanos of Bamidbar are designed to convey
HKB'Hs message, sometimes for us and sometimes for the nations of the
world.

The Vayikro reasons for the deaths of Nadav and Avihu relate to personal
shortcomings, so to speak, or misdeeds which they committed relative to
their extraordinary potential. They failed to draw as close as they could
and their misdeeds are therefore alluded to in Sefer Vayikro.

The Bamidbar reason for the death of Nadav and Avihu is that they lacked a
critical component in being qualified emissaries - they didn't marry and
father children. In order to be HKBH's emissary one must have a deep sense
of responsibility, and this is best gained by having a spouse and
children. Because this issue relates to their capacity as emissaries it is
alluded to in Sefer Bamidbar.